Electrolytical production of zinc or other metals.



m 629,685. Patented July 25, I899.

c. HOEPFNER. V ELEGTROLYTICAL PRODUCTION OF ZINC OROTHEB METALS.

(Application filed July 16, 1596.

(No Model.)

UNITLED STA ES-1' PATENT O F CARL HOEPFNER, or BERLIN, eERMAivY.

ELECTROLYTIC/u. PRODUCTION OF zfmo ,OR-OTHER METALS.

sincm'xoa'riori forming part of Letters Patent 629,685, dated July 25, 13992 Application filed .Tu1y16,1896. Serial No. 599,442. (No specimens.)

To all whon't it may c'onbef'n:

Be itknown that I, CARL HOEPFNER, asub-' ject of the King-of Prussia, Emperor of Germany, residing at No. 2 Helgolander-Ufer, Berlin, Germany, have invented certain new and useful Improvements in the Eleotrolytical Production of Zinc or other Metals, (for which Letters Patent have been obtained in France, No. 250,075, dated September 5,1895, and in Belgium, No. 117,278, dated September '5, 1895;) and I do hereby declare the following to be a clear and exact description of themvention.

This invention consists in improved methods for carrying out electrolytic decompositions in as rational and economical a manner as possible-i. 6., with the least possible electromotive force-especially such decompositions in which it is desired to obtain valuable products onlyfor example, where zinc or other metals, such as iron,nickel,or copper,are to be obtained from their salts by the electrolytic process at a moderate cost. I propose to' employ abath which for ordinary casesshould be divided by suitable membranes or diaphragms into anode and cathode cells in such manner that all the cells of like name will be connected in series through suitable conduits,

so that the electrolyte will circulate therethrough in a zigzag manner, flowing into the first cell of a series of such at the bottom and flowing out ofthe last cell at top, or vice versa, any suitable means being provided'for heating the electrolyte.

Apparatus such as referred to may be of any well known construction-as, for instance, of the construction shown and described in my British Letters Patent No. 13,735 of 1890 or as shown in the accompanying drawings, in which- Figure 1 is a horizontal section of an electrolytic apparatus or bath embodying the necessary conditions for carrying out my invention. Fig. 2 is a vertical transverse sec tion of one form of anode, and Fig. 3 is a transverse section between two cell-frames of an apparatus such as shown in Fig. 1.-

The cells are formed by a series of frames,

I of which I have shown eight, said frames being correspondingly numbered and are provided in their vertical members with passages or channels 00 1 2, so arranged that when said frames are clamped together between suitable headsh'h' by means of the. two rods S and clamping-bars or plates P the said channels will connect the cells of like name in series,

so that the electrolytes fed under suitable pressure to the anode and cathode cells will enter anode-cell 1 at top at a, rise therein, and

flow throughchannels a; y z to anode-cell 3, I

thence now through like channels on the inlet side of the apparatus to anode-cell 5, and

so on zigzag fashion from one anode-cell to another, flowingout at the inlet side of the apparatus from bottom of cell 7 at b. The

electrolyte for the cathode-cells Kfollows a substantially similar-course, entering at the top of first cathode-cell 2 at c and flowing from the bottom of the last cathode-cell 8 at d.

' The electrolytes are preheated in any suitable manner and their temperature kept up during the flow through the respective cells by causing such electrolyteas, for instance, the cathode-cell electrolyte-to flow from top ofcell 1 to a branch 0, connected with one of the terminals of a heater-coil at O, and

flowing back therefrom through a branch 0 connected with the other terminal of the coil C, which latterlis contained in a suitable heating-chamber O to which any desired heating'agent is supplied-as steam, for instance, entering at e and flowing out at f. A similar arrangement is or may be provided for heating the electrolyte for the cathodecells or for maintaining the preheated electrolyte. at the proper temperature.

A indicates the anodes, K the cathodes, and M the cell-diaphragms clamped between the cell-frames 2 3, &c.

The electrolyte or solution to be decomposed and supplied to the cathode-cells may, for example, be a solution of the metallic salt to be decomposed--such as chlorid of zinc, bromid of zinc, sulfate of zinc, nitrate of zinc, or acetate of zinc, or an alkaline solution of oxid of zinc, or similar solutions of other metals-while the cathodes will consist of carbon or any suitable metal in the shape of plates, disks, rods, or hollow bodies.-

It will be found very advantageous to actively maintain the cathode solution or lye at the cathodes in constant motion, for which purpose the cathodes are kept revolving or i2 1 y w .eaaes lye should be sufliciently concentratejcland kept warm and be made to circulate from an appropriate reservoir through the cell in a decomposition toa minimum (in fact, for

making it actually negative in the case of copper salts, for example) are not insoluble, but are soluble anodes consisting of metals or metalloidsubstances, while I take care at the same time that the solutions obtained therefroin do notreach the cathodes, but are prew cipitated from the anode lye in a harmless manner before they become too rich or abundant.

' The metals dissolved from the anodes are in fact made insoluble either chemically or physically, (or, in other words, 'iuany convenient manner,) and the resulting precipitates, which may be obtained within but should' be preferably produced outside the anode cell, are collected and utilized again forany useful purpose. As a rule they should be reducedt'.e., restored-to the me tallic state by means of carbon or other reducing substances, such as hydrogen or watergas, or by organic substances, as Wood or coal.

Themetal of the soluble anodes differs from the metal of the final product to be obtained at the cathode and is readily precipitable from its solutions, (like lead,) but is in soluble in diluted acid, (especially in diluted sulfuric acid,) so as to exclude, for instance, zinc and iron from the employment for the anodes. Such anodes, therefore, may preferably consist of lead or materials containing lead. These materials may be employed in the form of solid bars or plates or (especially in the case of sulfids) in a granulated or powdered condition, in which case the said material will be contained. in a holder or casing of wirefabric a or of perforated plates, as shown in Fig.2. In the latter case the electric current may be admitted through electronegative metalssuch as gun-metal, or copper-bronze, or silver wire-netting, or carbon rods, or the like-which should be retained in close contact with the pulverulent metals or sulfids. As to the anodes it is also better to keep them in motion, so as to facilitate the formation of a uniform solution and the employment of powdered sulfids, which otherwise might lose the contact.

The anodes are surrounded by an acid or a salt solution, which should preferably be heated, and the nature of which should be such that it will readily dissolve the compounds of lead formed electrolytically at the anode. The agents most suitable for the attainment of this object are solutions of chlorids, such as common salt, chlorid of calcium, chlorid of zinc, chlorid of potassium, or the like, or, more conveniently, nitrates or nitrites, such as nitrate of sodium or nitrate of zinc, or acetates, such as acetate of sodium or acetate of zinc, or acidsor salts capable of forming soluble compounds withlead. In order to enable this process to be keptnp in a regular manner for a comparatively extended period oftime, care must be taken to prevent the anodelye from absorbing too largean amount of le'ad.in no case more than from about fifty totoue hundred grams per liter'for if the quantity werelarger it would cause the voltage necessary for the decomposition to rise unduly, besides the lead, or instead of lead other metals which are used for and dissolved from the anode, would be readily diffused towa rd the cathode and there byimpair the purity of the zinc. Thelye, therefore, constantly circulates past theanodes and is freed in the course of this process within or, which is still better,-outside the bath from the whole or part of the lead (or other metal) which it contains. For the purpose of this precipitationof the lead from the anode lye any useful chemical precipitant may be used which is from the point of view of economy capable of precipitating lead from its solutions without. introducing other injurious matters into thesolution instead of such lead. i

In obtaining zincby this electrolytic process the following chemical agents will be found best suited for precipitating the lead from its solutions: sulfate of zinc, (Zn'SO chromate of zinc, (ZnCrO,,) sulfite of zinc, (ZnSO carbonate ofzinc, (ZnCO silicate of zinc, (ZnSiO oxid of zinc, (ZnO,) sulfid (or sulfuret) of zinc, (ZnS,) and chlorid of zinc. (ZnOl By means of any of these agents lead may be precipitated from solutions of chlorid, nitrate,or acetate in a very rational manner, and at the same time (by alternate decomposition) the lye Willagain be enriched with zinc, the reaction being as follows:

By means of pure oxid of zinc and carbonic acid white lead may be obtained. Instead of these zinc compounds where a cheaper solution of zinc is available and where, therefore, a regeneration of the zinc solutionsis not necessary other harmless precipitants may be utilized in precipitating the leadsuch as alkaline chlorids, bromids, chrom ates, sulfates, sulfites, sulfids, or similar compounds with alkaline earths, sulfureted hydrogen, ammonia, the alkaline earths themselves, carbonates, and sometimes acids, such as sulfurous or sulfuric acid and carbonic acid, and finally, also, oxid of lead, other lead compounds, such as hydroxid or carbonate of lead or substances containing oxid of lead, such as roasted lead ores, which will form a nearly insoluble basic salt when brought into contact with the salt of lead contained in the anode lye. In some casest'. e., where an inexpensive source of heat is available-the dissolved salt of lead may be precipitated simply by a physical process-A ia, by cooling, by diluting the soxco - will sutfice to effect the reduction;

chlorid of lead (and also chlorid of copper) may be reduced to the metallic state by means lution, or by the addition of anacid. -In or der to reliably preventa diffusion of lead from the anodes to the cathodes, sulfates'or; other substances capable of rendering, the salts of lead insoluble may be added to thecirculat ing cathode lye outside or inside the bath.

The lead compoundssnch'assulfate oflead, chlorid of lead, oxid of lead, or sulfid of lead-precipitated in' the manner hereinbefore described audwhich, as above ex- 'plained, may vary extensivelyin their nature may be utilized in any convenient manner in the manufacture of peroxid colors, (or dyes,)

glass, and'other substances. It is essential, however, to note (a fact already alluded to) that these compounds may be at a very small cost, indeed, restored-to-the metallic state by coal, hydrogen water-gas, or other reducing 'mediums such as natural sultids, (galena or iron pyrites, for example,) preferably sulfids or py-rites containing gold or silver.,and the lead may then be employed over again in the constant-circulation process as anodes.

. Supposing it is desired to reduce to the metallic state from its oxid two hundred and six kilograms-of lead, six kilograms of carbon Similarly chlorin, as well as sulfurous or sulfuric acid,

obtainable from the decomposition of chlorid or of sulfate or of sulfite of lead can be used over and over again for dissolving metallic- 'oxids, such as zinc oXid, and for regenerating the original solutions, foriustance, of zinc; In a similar manner it is possible to make 'use of the described lead-anode process for obt-ainingalso other metals by this electrolytic processsuch, for example, as nickel, manganese, chromium, and even alkaline metals or alloys or amalgams of the. same,

'which are more electropositive than lead.

On the other hand, this process is also available for the production of metals. which are more electronegative-Jor example, silver, copper, bismuth, iron, or the like, all of which may be obtained from their corresponding solutions. In this latter case a diaphragm is not absolutely necessary. I r

In the operation last described the lead, as in the extraction-of zinc previously de scribed, will likewise be separated from its solution--as, for instance, by means of compounds'of the corresponding metal to be obtained, and more particularlyby means of sulfates, sulfites, chromates, chlorids, and oxids, and thereby at the same time to maintain a uniform concentration of the metal contents of the lye.

' lead will constitute an excellent energy-save ,ing or volt-saving anode capable of reducing hall these cases the readily and reliably separated again, While at the same time, being readily fusible, it permits the metalto be regeneratedin a Very economical manner and in a solid or granulated state and renders theemployment of complicated filtering-machines in the precipitating'process unnecessary, inasmuch as the compounds of the lead are as heavy and readthe silver contained in argentiferous lead, (silver lead bullion,) if such'be used for the anode, can be readily and completely eX- tracted, since it'remains undissolved while the lead is being dissolved and separated.

Similarlyto lead, mercury, though it is much more expensive, may be utilized as an anode, inasmuch asit is still more readily recoverable as a metal from its components than lead isybutalthough lead appears to be the bestand most economical material for forming anodes which permit a considerable amount of electric energy to be saved and are at the same time capable of being readily regenerated, yet in some cases, especiallylwhere it is desirable that the anode be .ofsmall spe-' cific weight, other substances may be .employed as substitutes for lead. Among these may be instanccd, especially, copper; In that case also, however, it is absolutely neccoming too richly'impregnated with the metal dissolved therein. I This anode solution,which where the anodes are lead must not of course I be a solution of pure sulfate, may: in thecases just mentionedi'. e., where copper-is used-be a sulfate solution Without any inconvenience, since this metal is not insoluble as a sulfate; but in this case also the anode solution should not absorb more than from 'essary to prevent the anode solution from be fifty to seventy-five grams per liter of the disployed, provided they are capable of 'rernoving the metal dissolved at the anodes in. a

harmless and economical manner.

Inmany cases it will be sufficient to obtain a precipitate oflead or copper simply by the employment of lime or'magnesia, and the salts thus obtained,such aschlorid of calcium, may then be very readily utilized again, for instance, in the production ofchlorid of zinc from-oxid of zinc or carbonate of zincas,

for example, described in the specification of British Letters Patent No; 11,7 24 of 1894:. i

The employment of energy-saving anodes of lead orcopper or other easily reducible 75- 'ily settle as they are precipitated. Lastly,v I

'15. tro bodies are decomposed by the aid of lead metals or alloys thereof enables convenient electrolytic baths to be readily constructed and made to operate withla very lowelectromotive force. It has also alreadybeenstated above that energy-saving anodes, especially if the latter be lead, in some cases are capa ble of yielding a surplus of energy, (like gal vanic cells.) This applies more especially to those instances where the electromotive force required for the decomposition of certain fluids is less thanthe electromotive force set up by the act of dissolving the lead, which amounts to about 1.8 volts.

-ver or solutions of nitrates or nitrites or nianodes. Hence it follows that these energysaving anodes, especially lead, which is insoluble in diluted acids, but may be readily reduced from its compounds, mayfvery ad'- vantageously also be utilized as anodes inof coal'or water-gas or the like.

a The dynamic production of electricity has only hitherto utilized about ten per cent. of the energy inherent in carbonpwhereas the present process enables a far greater proportion of the energy thus generated to be satisfactorily turned to account. Two-thirds to three-fourths of the electromotive force necessary for chemical decompositions can henceforward be supplied by direct transformation of chemical into electrical energy.

Carbon foritself when directly transformed by electrolysis into oxid of carbon is not capable of furnishing more than .75 volt, whereas by the herein-described system it furnishes indirectly about two volts. Coal, moreover, has the drawback of being a non-conductor of electricity, whereas its substitute and product, the lead, is a good one. Lastly, conforming to this process, besides coal other sources of energy hitherto completely neglected, such as pyrites or galena, can be utilized.

Having thus described my invention, what I claim as new therein, and desire to secure by Letters Patent, is

1. A process which consists in placing a soluble metallic anode in a solution of a salt capable of dissolving the same, placing a suitable cathode in a second solution containing a metal other than that contained in the anode solution, separating the two solutions by a suitable diaphragm, passing a current, thereby bringing the anode metal into solution and Such is the case, for example, where the salts of copper or sildepositing the cathode metal, precipitating the anode metal-fromth'e anode solution and conveying the resulting solutiontothe cathode-compartment, substantially as described.

2. A process which consists in placing a soluble metallic anode in a solution offa salt capable of dissolvingthe same, placing a suitable cathode in secondsolution containing a metal other than that contained in'thean ode solution,-separating the two solutions by means of a suitable diaphragm, passing a current, thereby bringingytheanode metalinto solution and depositing the cathode metal,

precipitating the anode metal from the'anode solution by means of a cathode metal com-- pound and conveying the resultingsolution tothe cathodecompartment substantially as means of a zinc compound and conveying the resulting solution to the cathode-compartmen t, substantially as described.

4. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placinga suitable cathode in a solution similar to that at the anode but containing also zinc, separating the two solutions by a suitable diaphragm, passing a cur rent from the anode through both solutions to the cathode, thereby bringing lead or copper into solution at the anode and depositing zinc at the cathode, precipitating the lead .or copper dissolvedin the anode solution by acid ing a zinc compound thereto, and conveying the resulting solution to the cathode-compait ment, substantially as set forth.

5. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, separating the two solutions by a suitable diaphragm, maintaining their temperature above normal, passing a current from the anode through both solutions to the cathode, thereby bringing the lead or copper into solution at the anode, and depositing the zinc at the cathode, precipitating the lead outside the cells by cooling, and conveying the solution to the cathode-cell, substantially as set forth.

6. A process which consists in placing a lead or copper anode in a solution capable of dis solving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, separating the two solutions by a suitable diaphragm, maintaining their temperature above normal, passing a current from the anode through both solutions to the cathode, thereby bringing thelcad ICC or copper into solution at the anode, and depositing the zinc at the cathode, precipitating the lead by means of zinc carbonate outside the cells and conveying the resulting solution to the cathode-cell, substantially as set forth.

7. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, separating the two solutions by a suitable diaphragm, maintaining their temperature above normal, passing a current from the anode through both solutions to the cathode, thereby bringing the lead or copper into solution at the anode and depositing the zinc at the cathode, precipitating the lead by means of zinc oxid and carbonic acid and conveying the resulting solution to the cathode-cells, substantially as set forth.

8. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, separatingthe two solutions by a suitable diaphragm, maintaining their temperature above normal, passing a current from the anode through both solutions to the cathode, thereby bringing thelead or copper into solution at the anode and depositing zinc at the cathode, recovering the lead, treating a raw material containing zinc with the said solution, and conveying'the resulting solution to the cathode-cell, substantially as set forth.

CARL HOEPFNER.

Witnesses:

W; HAUPT, E. STEFFAHNY. 

